1. Field of Invention
The present invention relates generally to pneumatic tires and more specifically to heavy duty radial truck tires.
2. Description of the Prior Art
Heavy duty radial truck tires are often characterized by tread patterns utilizing ribs with projecting and reentrant portions in a generally zig-zag pattern. This tread pattern has proven advantageous for a variety of performance criteria. However, this tread pattern has also proven to be susceptible to a type of irregular wear known as "railway wear" or "river wear". River wear is wear in a circumferentially extending rib of a tire tread along the edge zones. The irregular wear spreads across the tread creating an unacceptable appearance and erosion of performance.
In the prior art, tread designers have sought to eliminate or reduce river wear by placing narrow slots in the edges of the tread ribs as in U.S. Pat. No. 4,449,540. Tread designers also modified projecting portions of the tread rib to prevent the initiation of river wear, as in U.S. Pat. Nos. 4,266,592 and 4,200,134. While these techniques have been moderately successful, river wear continues to be a significant source of irregular wear for truck tires used extensively for long distance highway applications.